Development of a new infrared device for monitoring the coefficient of variation in yarns



The coefficient of variation (CV) in yarns is the most important evenness characteristic in textile processing and quality control. This article develops a new infrared device for monitoring the coefficient of variation in yarns, based on on-line measurement of the yarn diameter, during the yarn manufacturing process. The device is composed of a 555 astable oscillator, four pairs of infrared emitters and receivers, a summing amplifier, an inverting amplifier, an alternating current (AC) to direct current (DC) converter, a unity-gain second-order Sallen–Key low-pass filter, and a data acquisition system. The optimum values of some factors with the circuit, including the oscillator frequency, amplified gain, cutoff frequency of the low-pass filter, sampling time, and number of sampling data to be averaged in the moving average method, are systematically chosen by the Taguchi method to reduce the variance in the output voltage of the device. The CV based on measured yarn diameter data is transformed to that based on mass profiles. The experimental results reveal that the CVs evaluated by the infrared device are close to those by the Uster Evenness Tester, which is verified by the statistical analysis of variance. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007